Means for recording or indicating electrical impulses



Oct. 5, 1937. FfB. CARD ,7

MEANS FOR RECORDING OR INDICATING ELECTRICAL IMPULSES Filed Dec. 28, 1933 I 125 ,4- Ii n m/az/r BAFFLE lfifQUi/VC) INVENTQR Fdill-ffi 5. 04/?0 A TTORNEY Patented Oct. 5, 1937 MEANS roa nncoanmc on INDICATING ELECTRICAL IMPULSES Foster B. Card, Los Angeles, Calif., assign... to

Radio-Keith-Orpheum Corp., a corporation of Maryland Application December 28, 1933, Serial No. 704,263

4 Claims.

This invention relates to the recording or indicating of electrical impulses, and has for its principal object the provision of an improved apparatus and method of operation whereby the amplitude effect of such impulses at resonance frequencies may be limited or controlled to have any desired value.

A mechanical system including movable parts L and subjected to a range of operating frequencies tends to respond unequally to impulses of different frequencies due to the fact that it possesses a natural or free vibration frequency. Thus an indicating or recording instrument such as a galvanometer has a free vibration period or resonance frequency which causes it to respond more strongly to certain frequencies than others. This results in a non-linear response of the device to actuating impulses of diflerent frequencies. In order to correct this inherent defect, it has Q been customary to immerse the moving element in a damping fluid or liquid of a consistency calculated to minimize the response of the device withinthe range of resonance frequencies. Thus where the movable element is immersed in oil, it is customary to choose an oil of such viscosity as to minimize the resonance effect and produce a linear relation between the frequency and the response. This'method, however, has the disadvantage that the oil must be changed and can not always be relied upon to produce the exact degree of compensation to produce the desired result.

In accordance with this invention, this difliculty is avoided by the provision of a mechanical element, such as an adjustable baiile, for controlling the movement of the fluid or liquid wherein the movable member or members of the device is mounted. The damping effect may of course be produced by any suitable fluid or liquid such as oil, air or the like.

The invention will be better understood from 'the following description when considered in connection with theaccompanying drawing'and itsscope will be pointed out in the appended "claims.

Referring to the drawing: Fig. 1 illustrates an impulse recorder in the improved device is utilized, n

' Fig. 2 is a side view of the device, Figs. 3 and 4 illustrate constructional details of the device, and

.Fig. 5 is an explanatory diagram relating to the operation of the device. g 55 1.The apparatus of Fig. 1 is readily recognized which as a device for photographically recording sound on the edge of a motion picture film 0r the like. It includes a light source In from which light is projected through a'lens II, a light stop I2 and a lens It to a mirror i4 mounted on a looped vibratable electrical conductor l5. Both the mirror M and the conductor l5 are mounted in a suitable damping fluid such as oil, air or the like. From the mirror l4, 'light is reflected to a photographic recording surface through the lens i3, past the edge of a gage I1 and through the lenses l8 and I9, the light slit 20 and the objective 2!. It will be readily understood that the conductor i5 is subjected to any appropriate magnetic field, that the mirror It vibrates transversely of the direction in which the record I6 is moved and that the exposed area of the record is proportional to the amplitude of the electrical impulses applied to the conductor it. As appears more clearly in Fig. 2, the impulses to be recorded are applied to the conductor i 5 through terminals 22 and this conductor extends through a member 23, a clamp 24 and over supports 25 and 26 to a pulley 21 which forms a loop midway between the ends of the conductor. These various parts are so constructed and arranged as to ensure that the conductor is properly insulated, and are mounted on a base 28.

For the purpose of regulating the tension of the conductor IS, a screw 29- is threaded into the member 23 and arrangedto contact with the left hand end of'a tension rod 30 extending through the members 24, 25 and 26 and provided at its right hand end with'a" member 3| arranged to contact with a pulley support "32 pivoted orl otherwise suitably attached to the base 28 at the P int 33.

As indicated in Figs. 3 and 4, the tension rod 30 is slotted at 34 to receive .a baflle 35 which may be adjusted with respect to the mirror II and .the conductor I5 on which it is mounted.

The effect of this bafile is shown by the curves of Fig. 5. Thus without the baflle and with a relatively heavy damping oil, the amplitude-of the response in the resonant frequency range is substantially double that in the non-resonant frequency range. With the baflie, this non-linear effect is greatly minimized. It will be apparent that any desired peak amplitude between the limits indicated by the two curves of Fig. 5 may be produced by adjustment of the baflle 35. The smaller the spacing between the baflie edgesv and the surrounding surfaces of the mirror It and the Bakelite surfaces of the members 25 and 26, the greater is the baflling eifect. A suitable form of baiile is a folded strip of .005 inch phosphor bronze sheet. It will be apparent that adjustment of the position of the baflle may be effected either directlyor by means of a suitable adjusting member mounted outside the casing of the apparatus. The use of a lighter damping fluid of course makes possible a greater range of amplitude adjustment at a higher frequency for the same sensitivity.

Having thus described my invention, I claim:

1. The combination of means vibratable in response to electrical impulses, a fluid medium surrounding said means, and a baflle member having an edge extending adjacent to said means arranged to control the efi'ect of said fluid on the vibrational amplitude of said means at a predetermined range of frequencies.

2. The combination of means vibratable in response to electrical impulses, a fluid medium surrounding said means, and an a fiustable baflle arranged to control the eflect of said fluid on the vibrational amplitude ofsald means at a predetermined range of frequencies. -3. The combination of light reflecting me vibratable in response to electrical impulses, a body of oil surrounding said means, and a member immersed in said body having an edge extending adjacent to said means and coacting therewith to vary the vibrational amplitude of said means at a predetermined range of frequencies. 

